298 TEXTBOOK OF ZOOLOGY 



A group of mites belonging to the family Tetranychidae, known as 

 brown mites and red spiders, are widely distributed, feeding upon 

 practically all kinds of cultivated plants. The clover or brown mite, 

 Bryohia praetiosa, is cosmopolitan in distribution. It feeds upon 

 fruit and shade trees, garden plants, and common annual and peren- 

 nial plants. The common red spider, Tetranychus telarius, which is 

 common in this country, attacks field plants, fruit trees, forest trees, 

 shade trees, and shrubs. It is reported that it attacks over 250 

 species of plants. Another common mite pest is the leaf blister mite, 

 Eriophyes pyri, which belongs to the family Eriophyidae. This 

 species attacks the leaves of the pear and apple. The damage to the 

 leaves results in the development of brownish blotches and partial 

 defoliation. 



The ticks are all fairly large parasitic species. Those belonging 

 to the family Argasidae attack only warm-blooded animals. After 

 taking a meal of blood, they leave the animal and go into hiding. At 

 times they are a serious pest to poultry. Ticks of the family Ixodidae 

 attach themselves to their host, suck blood, and grow to many times 

 their original size. Texas cattle fever and Rocky Mountain spotted 

 fever are dreaded diseases that are carried by ticks. 



The order Scorpionida consists of large-sized arachnids with pedi- 

 palpi which resemble the chelipeds or pinchers of the crayfish; also 

 with a flattened body and elongated abdomen terminating in a 

 specialized stinging organ. They are nocturnal, hiding during the 

 day under rocks and burying themselves in the sand. They feed upon 

 insects and spiders. 



They are viviparous; the mother takes care of the young, protect- 

 ing them by carrying them around on her back and by helping them 

 to catch their prey. They breathe by means of lung books and have a 

 direct development like the spiders. A peculiar comblike structure, 

 called the pectine is found in the ventral part of the second ab- 

 dominal segment. Four families are represented in the United States, 

 and they are found only in the southern and western states. Had- 

 rurus hirsutus, and Vejovis mexicanus of the family Vejovidae are 

 common species. 



Another interesting little group of arachnids is the order Solpugida, 

 found in the same territory as the scorpions and represented by 

 twelve species contained in three genera. Eight of the species be- 

 long in the genus Eremohates. 



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